linux-kernel - Re: [PATCH v3 2/4] gpio: pca953x: add register definitions for pcal6524 and fix address calculation

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Message-ID: <CAHp75VfYk1tSJ9PUshDvY2RaYrc+wR+hyrK8Ck1oQSUXPr-0fQ@mail.gmail.com>
Date:   Tue, 10 Apr 2018 21:06:41 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     "H. Nikolaus Schaller" <hns@...delico.com>
Cc:     Kumar Gala <galak@...eaurora.org>,
        Rob Herring <robh+dt@...nel.org>,
        Pawel Moll <pawel.moll@....com>,
        Mark Rutland <mark.rutland@....com>,
        Ian Campbell <ijc+devicetree@...lion.org.uk>,
        Linus Walleij <linus.walleij@...aro.org>,
        Alexandre Courbot <gnurou@...il.com>,
        devicetree <devicetree@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>, kernel@...a-handheld.com
Subject: Re: [PATCH v3 2/4] gpio: pca953x: add register definitions for
 pcal6524 and fix address calculation

On Tue, Apr 10, 2018 at 7:07 PM, H. Nikolaus Schaller <hns@...delico.com> wrote:
> PCAL chips ("L" seems to stand for "latched") have additional
> registers starting at address 0x40 to control the latches,
> interrupt mask, pull-up and pull down etc.
>
> The constants are so far defined in a way that they fit for
> the pcal9555a when shifted by the number of banks, i.e. multiplied
> by 2.
>
> Now the pcal6524 has 3 banks which means the relative offset
> must be multiplied by 4 which gives a wrong result if not done
> carefully, since the base offset is already included in the offset.
>
> For the basic registers shared with all pca93xx/tca64xx chips
> there is no such offset.
>
> Therefore, we add code to adjust the register number for exended
> registers to the 24 bit accessor functions.
>
> And we add additional register offset constants (not yet used by
> the driver code) which are specific to the pcal6524.
>

First of all, as I said, please split this to two patches. Don't mix the things.


> +       /* adjust register address for pcal6524 */
> +       if (reg >= PCAL953X_OUT_STRENGTH)
> +               reg -= PCAL953X_OUT_STRENGTH >> 1;
> +

Give me some days to think about it.

-- 
With Best Regards,
Andy Shevchenko